In central Illinois, overnight lows Monday are expected to drop below zero and could reach 12 below. In northern Illinois, temperatures may fall to between minus 15 to minus 20 later Monday into Tuesday morning.

Forecasters say the weather pattern that's brought the repeated arctic assault to the Midwest is unusual. In central Illinois, most areas are on track to record one of the top 10 coldest winter seasons on record.

The National Weather Service says the Monday morning wind chill was 39 below zero at Aurora Municipal Airport. In De Kalb, the wind chill dropped to 32 below zero. In Kankakee, the wind chill was negative 35.